The present invention relates to a sealing composition and a sealant, and more particularly to the sealant which is used preferably for an etching apparatus which is used in the field of semiconductor and liquid crystal display devices.
With the miniaturization and high integration of semiconductor devices and with the increase in the size of liquid crystal display devices and sophistication thereof, dry etching is used as a key technology for miniaturizing the semiconductor devices and sophisticating the liquid crystal display devices. That is, replacing wet etching, dry etching has become increasingly important as a technique of processing fine lines and thin film transistors of the liquid crystal display devices.
Dry etching is classified into reactive plasma etching which is performed, utilizing only chemical reactions of active particles in plasma generated by applying a high-frequency electric field to gas introduced into a chamber; unreactive ion etching which is performed, utilizing only sputtering action caused by ions accelerated by an electric field; reactive sputtering etching which is performed in combination of the reactive plasma etching and the unreactive ion etching. In order to perform the above etching method, the following etching apparatuses have been developed: a plasma etching apparatus, a reactive ion etching apparatus, a reactive ion beam etching apparatus, a sputtering etching apparatus, and an ion beam etching apparatus. Further, a multi-chamber system for successive processing has been developed.
In the etching process which is carried out using the above-described etching apparatuses, there occur V.sub.th shifts, leaks, increase in the resistance of contacts, corrosion of Al wiring all due to the presence of heavy metals and contamination due to the adherence of polymer to parts of the etching apparatuses, thus causing the deterioration in the quality of semiconductor devices, substrates of liquid crystal display devices, and the deterioration in the yield of product.
Therefore, in order to maintain the quality of the semiconductor devices and that of the substrates of liquid crystal display device, the etching apparatuses are checked and repaired periodically. Normally, the checking and repairing time is determined by the characteristics, strength, and the like of sealants such as a gate valve sealant and a peripheral sealing material. That is, metal ions eluted from sealants affects the yield greatly. This tendency is outstanding in the ion etching apparatus required to be operated in pressure-reduced atmosphere.
The following sealing compositions are known.
A copolymer consisting of tetrafluoroethylene, perfluoromethylperfluorovinyl ether, and monomer having curing portions (disclosed in Examined Japanese Patent Public No. Hei4-81609); and a copolymer containing at least one kind of unsaturated compounds having the property of ethylene and fluorovinyl ether (disclosed in Examined Japanese Patent Publication No. Hei5-63482).
Sealants such as O-rings, peripheral sealants, and the like formed by molding the above-described copolymers containing fluoroalkyl vinyl ether type do not have the high strength requirements of the etching apparatus. It is possible to improve the strength of the above-described copolymers by adding carbon black thereto, but the sealants formed thereof are electrically conductive and thus cracked in the plasma etching apparatus. In order to solve the above-described problems, a sealant containing silica powder used as a filler has been developed. But a lot of a content of metals, especially, a lot of a content of barium is eluted from the sealant, which necessitates checking/repairing of the etching apparatus at short intervals. Thus, the yield of semiconductor devices and substrates of liquid crystal display devices cannot be improved.
Further, the conventional sealant has a problem that it is in capable of maintaining its initial characteristics for a long time when it is used in a high energy-consuming environment, with the recent remarkable progress in the performance of the etching apparatus.